### <div class=phishy>Introduction</div>

The term "Evolution" is not entirely new in this era; particularly the concept of human evolution. Before now, we have seen how the present day humans evolved overtime from some weird-looking hominid Ape-like species. But another question has arisen; "is the process of evolution always continuous and forward, or is there a possibility of a backwards movement?". In this post, we will be looking at the concept of human de-evolution and taking some examples that could point us to the right direction.

https://i.imgur.com/MBphUQb.jpg

[Image Source: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Human_devolution_scheme.JPG). Author: Autoren der angegebene. [CC BY-SA 1.0](https://creativecommons.org/licenses/by-sa/1.0/deed.en) Licensed]

### <div class=phishy>Is there a particular limit to our evolution? Wassup with evolution?</div>

Evolution has been seen as some structural adaptative changes that occur in an organism in response to some factors (environmental, biological, or physical), which can also be trailed by the subsequent generations. Most importantly, one of the needs of evolution is to ensure the survival of species. Okay, here's a spoiler's alert: `According to this` [report](https://www.sciencedaily.com/releases/2004/08/040816001443.htm), `it was indicated that about 99% of the entire species that have walked on this planet have now gone into extinction (and that includes the ancestral lineage of modern man)`.

If this is so, that means; the word "adaptation of species" belongs rather to the grey zone. This is because, palaeoanthropologically, human evolution occurred, not necessarily to ensure the full survival of species, but also in response to some environmental factors. Just like it was indicated in the theory of "Use and Disuse" by Jean Baptiste Lamarck:

> An individual lose traits they do not use... - Jean Baptiste Lamarck

In the same way, an individual will consolidate more on the traits that is needed and used often. An example is this: `Our ancestors were majorly tree-dwellers, so their feet were adapted for grasping tree branches. But as time went by, the need for tree-dwelling was shifted to walking on the ground, and they started evolving with a flatter feet`.

One of the characteristic changes that occurred overtime during the timeline of human evolution from their ancestors was the increase in brain size; but how has this turned out in this era?

https://i.imgur.com/JkuGy6D.jpg

[Image of Primitive skulls. Source: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Primate_skull_series_with_legend.png). Author: Christopher Walsh. [CC BY-SA 2.5](https://creativecommons.org/licenses/by-sa/2.5/deed.en) Lisensed]

### <div class=phishy>Evolution cum De-evolution in brain size</div>

As the earliest ape-like hominid species evolved, the brain was seen to be bigger in size; according to fossil studies (which, no doubt, indicated an increase in cognition, intelligence, and other psychomotor abilities), no wonder, as they evolved, they made use of complex stone tools.

Take this example: One of the ancestors of modern men; the Australopithecus, had a brain mass of almost half of the average of the present day humans [[ref](http://www.indiana.edu/~brainevo/publications/schoenemann-hominid-brain-evol-2013.pdf)], not to mention the earlier Sahalantropus that had even smaller brain mass. But the Pithecanthropus that evolved later had a much larger brain when compared to their direct ancestors. No wonder they were wiser than their grandpas. Okay, the truth is; this trend continued.

But a shocking revelation was made by this [publication](http://www.ancient-origins.net/news-evolution-human-origins/scientists-are-alarmed-shrinking-human-brain-001446). It has been indicated that there is a slight decline in the average volume and mass of the brain of the modern human specie over the last 30millenia (the figure was placed at a decline from the average of 1500cm3 to an average of 1300cm3). Okay look at this trend holistically; if the evolution of humans from the ancestral hominid species was partly characterized by an increase in brain size, what would you call the scenario that the brain mass is going on a reverse gear?

Now you may wonder; why is the brain dwindling in mass and volume? Obviously, the answer lies not far from the question. In this era, there has been heavy reliance on computational devices and even memory devices, and the need to stock in much info in our brain has almost been overridden, thus giving rise to some forms of dormancy (or I should say; inactivity), and of course, the theory of "use and disuse" would come into play. By inference, this can be a pointer to a reverse evolution (de-evolution).

The decrease in brain mass does not mean we are dumbasses like our ancestral grandpas, but judging by our advancements in the last couple of decades, it should be disturbing that humans are, in fact, losing some cognitive abilities. Okay, away from the brain mass, let's look at another irregularity in the timeline of human evolution.

### <div class=phishy>Evolution cum De-evolution in height and size</div>

Based on paleontological studies of fossils, it was proven that the Australopithecus I mentioned earlier stood at an average of 3.5feet [[ref](http://www.columbia.edu/itc/anthropology/v1007/2002projects/web/australopithecus/austro.html)], which was seen to increase as they evolved into newer species, then it got to the Homo Habilis (which stood at the average of 4.3ft), and also to the Homo Erectus; the upright man; which had the average height of 5.8feet [[ref](http://humanorigins.si.edu/evidence/human-fossils/species/homo-erectus)].

But awesome enough, in-between the Homo erectus and the Homo habilis, there was a specie that existed, which is **Homo ergaster**. What's so special about this guy? Okay; it stood at the average of 6.2feet. Are you deducing anything? Okay just hang on.


https://i.imgur.com/vGFhL36.jpg

[Homo ergaster. Source: [Flickr](https://www.flickr.com/photos/jsjgeology/15278533828). Author: James St. John. [CC BY 2.0](https://creativecommons.org/licenses/by/2.0/) Licensed]

If you look closely to the example I gave, you would agree with me that there was a characteristic surge and swing in the size of some of the ancestors of modern man. It is not surprising that some fossils have been exhumed, which were well over 8feet in height [[ref](https://redice.tv/news/a-giant-mystery-18-strange-giant-skeletons-found-in-wisconsin-sons-of-god-men-of-renown)]; even as large as some monsterous 36feet extinct human-lookalikes. And based on carbon dating on the fossils, they lived long after the era of the primitive Australopithecus and the Sahalantropus. But now, the average height of the Homo sapiens sapiens is at somewhat of 177cm (for men) [ref](https://www.medicalnewstoday.com/articles/318155.php). The question is; did we get to a certain limit and started going back again? In order words; is the fluctuation in height evidential in proving the concept of de-evolution?

https://i.imgur.com/1OI624L.jpg

[Image Source: Screenshot from the [YouTube Video](https://youtu.be/dbIc6UUAbRg). 22second from start. Author: Billschannel]

### <div class=phishy>Evolution cum De-evolution in life expectancy</div>

In the [Paleolithic era](https://en.m.wikipedia.org/wiki/Paleolithic); which was also the era of the ancient hominid species (Homo habilis and brethren), the average life expectancy was at the average of 33years [[ref](https://en.m.wikipedia.org/wiki/Life_expectancy)]. The figure swung to 20years for the [Neolithic era](https://www.britannica.com/event/Neolithic-Period) . Then during the early medieval era, the life expectancy increased to over 35years and dwindled again to 30years for the late medieval era [[ref](https://en.m.wikipedia.org/wiki/Life_expectancy)].

But according to this [source](http://data.worldbank.org/indicator/SP.DYN.LE00.IN), the average life expectancy as at 2014 was pegged at 71.5years. But you would agree with me that in the last century, people lived way older than what we have in this era. The reason could be related to our eating pattern and dependence on processed food. Okay, these fluctuations in the average life expectancy can also point to the fact that evolution can also move in a sinusoidal manner, and not necessarily the forward trend we have been made to believe.

But the question is; with all these evidences, would it be possible to return back to the primitive stage? Well, I leave you with the assumptions of Dr Ray Lankester; in one of his books on Degeneration; after some experimentations with sea squirt, he came to a deduction that it is not impossible for a higher life form to degenerate into a simpler form. Now, if this is possible, why do we think de-evolution wouldn't be possible?

### <div class=phishy>Conclusion</div>

We have been made to believe that "evolution" is based on forward progression of adaptation in the nature and traits of organism, but as it were, there have been some swings in this progression. Just like we have talked about. Maybe we have just seen that it is not impossible that the trend of evolution can actually follow the same path back to where it all started.

***Thanks for reading***

> References for further reading:

- [humanorigins/human-fossils](http://humanorigins.si.edu/evidence/human-fossils/species)
- [Hominid-Brain-Evolution.pdf](http://www.indiana.edu/~brainevo/publications/schoenemann-hominid-brain-evol-2013.pdf)
- [Human_Brain_Decline](http://www.ancient-origins.net/news-evolution-human-origins/scientists-are-alarmed-shrinking-human-brain-001446)
- [Life-expectancy](http://wholehealthsource.blogspot.com/2008/08/life-expectancy-and-growth-of.html)

<div class=phishy> If you’re in the field of science, technology, engineering, or mathematics, you can join SteemSTEM community in the discord:</div> https://discord.gg/mKSKQ7T 

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